Floating systems, especially mooring buoys, for anchoring to the sea-bed

ABSTRACT

The system comprises a floating body such as a buoy or barge, connected to an anchoring base by at least one arm articulated to the base by a universal joint. The inclination of the arm can then vary according to the wind and current. Preferably the buoy is rigidly fixed to the arm. The inclination of the arm is particularly in the range 20* to 45*. The buoy may be flat and bear equipment such as winding drums for a flexible tube, for instance connecting a petroleum tank on the sea-bed to a ship. A pump may be arranged for actuation by the swell to drive equipment on the buoy through a hydraulic motor.

United States Patent Leeomte Nov. 27, 1973 FLOATING SYSTEMS, ESPECIALLY 3,472,293 10/1969 Bily.... 114 230 x MOORING BUOYS, FOR ANCHORING o 3,461,924 8/1969 B11y 1 14/230 X 2,863,293 12/1958 Plumer 114/05 D THE SEA-BED Inventor: Claude M. Lecomte,

Fontenay-aux-Roses, France Assignee: Entreprise DEquipements Mecaniques et Hydrauliques E.M.H., Paris, France Filed: Oct. 2, 1972 Appl. No.: 294,162

Related US. Application Data Continuation of Ser. No. 32,568, April 28, 1970.

Foreign Application Priority Data References Cited UNITED STATES PATENTS 3/1973 Gratz 9/8 P X Primary Examiner-Milton Buchler Assistant Examiner-Gregory W. OConnor Att0rney-Fleit, Gipple & Jacobson 5 7 ABSTRACT The system comprises a floating body such as a buoy or barge, connected to an anchoring base by at least one arm articulated to the base by a universal joint. The inclination of the arm can then vary according to the wind and current. Preferably the buoy is rigidly fixed to the arm. The inclination of the arm is particularly in the range 20 to 45. The buoy may be flat and bear equipment such as winding drums for a flexible tube, for instance connecting a petroleum tank on the sea-bed to a ship. A pump may be arranged for actuation by the swell to drive equipment on the buoy through a hydraulic motor.

Patented Nov. 27, 1973 3,774,253

10 Sheets-Sheet l INVENTOR ClduJa M. Lecomk ATTORNEYS Patented Nov. 27, 1973 3,774,253

10 Sheets-Sheet 2 Patented Nov. 27, 1973 10 Sheets-Sheet 5 Patented Nov. 27, 1973 10 Sheets-Sheet 4 Patented Nov. 27, 1973 I 3,774,253

10 Sheets-Sheet 5 Patented Nov. 27, 1973 3,774,253

10 Sheets-Sheet 6 Patented Nov. 27; 1973 10 Sheets-Sheet 7 Patented Nov. 27, 1973 10 Sheets-Sheet 8 Patented Nov. 27, 1973 3,774,253

10 Sheets-Sheet 9 Patented Nov. 27, 1973 '10 Sheets-Sheet 10 FLOATING SYSTEMS, ESPECIALLY MOORING BUOYS, FOR ANCHORING TO THE SEA-BED This is a continuation, of application, Ser. No. 32,568, filed Apr. 28, 1970.

The present invention relates to improvements in floating systems especially of the type of mooring buoys, for anchoring to the sea-bed or the like.

More particularly the invention relates to the floating systems intended to be anchored with respect to a seabed or the like (or to an undersea assembly, for example a submarine storage reservoir); to such systems as mooring buoys, barges or other boats with a relatively flat bottom; and it relates more particularly again, to systems of the type for petroleum installations, especially to ensure the momentary mooring of oil tankers and more especially to ensure the transfer of petrol from storage reservoirs (particularly submarine) to these ships or conversely.

It is current practice to connect these floating systems, especially buoys, to an ocean floor by anchoring chains. But this solution has various drawbacks and especially, by reason of the large movements they undergo, rapid wear of the anchoring chains as well as rapid wear of the flexible equipment for loading petroleum, in the case where the mooring of oil tankers is concerned.

It is therefore an object of the invention to improve the stability of the buoys or floating systems of this type, by means of a novel method of fixing.

The invention proposes to arrange systems of the type concerned so that the floating part is connected to the anchoring base (fixed to the submarine floor or again fixed on a submarine reservoir), by at least one arm articulated to the latter and having normally, taking into account the depth of the anchoring floor, a predetermined inclination (for example selected of the order of 20 to 45 or more, as the case may require) the articulation of the said arm being preferably double, that is to say, on one hand, around a horizontal axis and, on the other hand, around a vertical axis, so that the inclination of the arm can vary as a function of the forces, both hydrostatic and mechanical, applied to the floating part and that in addition the arm can be oriented with respect to the vertical pivoting axis, especially according to wind and current.

It comprises, apart from this main feature, certain other features which are used preferably at the same time, and which will be more explicitly described be low.

In order that the invention may be more fully understood several embodiments of floating systems accord ing to the invention are described below purely by way of illustrative but non limiting examples, with reference to the accompanying drawings in which:

FIG. l shows in diagrammatic elevation one embodiment of a system for mooring buoys constructed according to the invention;

FIGS. 2 and 3 illustrate diagrammatically two variations of the embodiment of FIG. 1;

FIGS. 4 to 6 show in schematic manner, respectively in elevation, in partial side view and in plan view showing only the buoy, an embodiment of a buoy mooring system with transfer of liquid from a reservoir (well, etc.), said system being constructed according to the invention;

FIG. 7 shows in elevation another embodiment of a system of the same type according to the invention;

FIG. 8 shows similarly and partially a variation of the embodiment shown in FIG. 7;

FIG. 9 shows in diagrammatic elevation another embodiment of a system of the same type, with automatic actuation of the drum;

FIG. 10 illustrates diagrammatically another embodiment according to the invention;

FIGS. 11 and 112 show in diagrammatic manner, respectively in elevation and in partial plan view, a barge anchored according to the invention.

FIGS. 13 and 14 show in diagrammatic elevation respectively in a transporting position and in assembled position, a buoy mooring system constructed according to another embodiment of the invention;

FIGS. 15 and 316 show respectively, and partially, in elevation and in diagrammatic plan view, the assembly of an oil tanker and a mooring pontoon anchored and constructed according to the invention.

FIGS. 17 and 18 show similarly an assembly of the same type, in which the pontoon has become an unloading quay.

FIG. 19 shows in diagrammatic elevation a mooring buoy constructed according toanother embodiment of the invention; and

FIGS. 20 and 21 illustrate similarly and partially a similar arrangement, of an embodiment, in the application of the invention to a barge, respectively according to two variations.

According to the invention and more particularly according to those of its methods of application, as well as according to those of its methods of construction of its various parts to which it would appear that preference should be given, in order, in a general way, to anchor a floating body with respect to the ocean floor, especially of moderate depth H (for example down to 30 m and even deeper), which floating body is intended to be subjected to the effect of swell as well as to mechanical forces which will be assumed to be, in the application (which will be first described by way of example) to mooring buoys for oil tankers or the like, tractive forces on the mooring cable, procedure is as follows or in similar manner. i

The floating body, particularly the mooring buoy 1 (FIG. 1), is connected to an anchoring base 2 fixed to the sea-bed 3 (or for example also to a submarine storage reservoir), by at least one arm 4 to which the said buoy is preferably rigidly fixed whilst it is articulated on the said base, the assembly being effected so that for the normal floating position, the said arm has, with respect to the vertical axis Z Z of the anchoring point, a certain inclination A, selected for example in a certain range of the order particularly of 20 to 45 or even as the case requires (especially 30).

In such an assembly, the tractive force F, applied by the ship on the cable 5 fixed to the mooring post such as 6, tends to increase the angle inclination A, by making the arm A pivot around its horizontal axis of articulation 7 (as indicated in discontinuous line, in very exaggerated fashion, in FIG. 1), but this variation is counterbalanced by the increase in the hydrostatic thrust on the floating body 1 which is urged to be immersed. It is noted that this correcting reaction is all greater as the angle A is selected initially and by construction, to be greater. For a suitable angle, which it will be up to the operator to determine, the variations remain very limited.

In addition, the effects of the swell will also be relatively limited, and the buoy will in any case be stable, in the case represented both in FIG. 1 and in FIGS. 2 to 9, where the floating body is rigidly fixed to the arm 4.

The effects of swell are a function of the shape of the floating body. They are of greater magnitude on a body or buoy of flat form such as that of FIG. I, a form which is obviously advantageous to ensure easy access on the buoy, as well as for convenience of mounting various equipment. They are less important for a floating body of vertical shape, such as shown in FIG. 2, with an upper platform, 8, but on the other hand plunging, under the effect of variation in load arising either from the force F or from the variation of vertical loads applied to the buoy, is greater. Hence it is convenient for the technician, in each case, to determine the most suitable shape. FIG. 3 shows an intermediate solution comprising, at the base of the vertical column constituting the body 1, a compensating float element 9.

Whatever the embodiment adopted, it will be convenient to provide, the base of the arm 4, a double articulation, namely:

on one hand, the above-mentioned articulation with horizontal axis 7, and, on the other hand, a device for pivoting around a vertical axis Z Z.

This device will generally be indispensable to enable the assembly to orient itself freely in the wind, and without any secondary reaction or any difficulty of mooring resulting.

There may thus be produced assemblies in which the floating body or the buoy 1, offers great stability and enables the installation of any of a variety of apparatus such as: signalling or reference masts, meteorological measuring instruments, etc., crews quarters, bridge area, storage of supplies and, especially as illustrated in FIGS. 4 to 6, winding drums.

The said FIGS. 4 to 6 show a buoy 1 provided with two winding drums 11 for flexible members 12 intended for the transfer of petrol and capable of being connected to at least one supply pipe 13, which can come for example from a storage reservoir on the mainland or the submarine floor, from a petroleum well, etc. Rotary joints such as 14 and 15 are provided at the base to enable free pivoting of the arm; a connecting pipe 16 running the length of the arm ends at the drums 11.

The mooring post 6 is arranged in the usual manner. The volume of the buoy 1 is compartmentalized to receive auxiliary equipment such as an electrogenerator or hydraulic assembly, pumps, etc.

There is seen in FIG. 4 one of the possible embodiments of the pivot with the vertical axis 10. This pivot is arranged in a form of rollers of a rotary plate, which rollers are interposed between a base 17 receiving the articulation 7 and a bottom plate I8 which is fixed to the bed plate 2 anchored to the bed.

It is to be noted that, to limit risks of collision, a pointed outer defence, on the mooring side, may be provided to facilitate the throwing off of the buoy from one edge or the other of a ship colliding with the surface.

FIGS. 7 and 8 illustrate other solutions capable of being used for the production of rotary joints between the supply pipe and the buoy.

In the embodiment of FIG. 7, the oil tanker pipe 13 rises vertically, along the axis ZZ, following an extension 19 including, at its base, a flexible pipe 20 to enable oscillations of the arm 40 to be followed. This extension l9,may be borne by a framework 21 rigidly fixed to the buoy l with, if necessary, a windbrace arm 22. An intake tube 23 connected by an elbow 24 to the extension 19 ends at the buoy. In this solution, there exists only one rotary joint at 25.

In the embodiment of FIG. 8, the rotary joint 14 is preserved, but there is provided a flexible linkage 26 between the joint 14 and the pipe 16.

In such devices, the manipulation of the winding drums for the flexible tubes 12, in the same way as the manipulation of any equipment members, can be done by means especially of hydraulic mechanisms supplied by a central station installed in the float.

However, taking into account especially that the recovery of the flexible members is not indispensable, as in the case of bad weather, there may be envisaged, according to another feature of the invention, having recourse, for supplying these mechanisms, to a pump operating by means of the swell.

In particular, according to an embodiment shown in FIG. 9, reliance may be placed on such a pump with means operable as a function of the articulation of the arm 4.

In this FIG. 9, the drum 11 is placed in action by means of a hydraulic motor system shown at 27. This motor 27 is supplied from a hydraulic tube 28 connected to the said motor as well as to an oil reserve 29, this pump having its piston or other member similar thereto actuated by a connecting rod 30 linked to a fixed point 31.

It is seen that the oscillations of the arm 4 have the effect of ensuring the manipulation of the said connecting rod and, consequently, the actuation of the pump and the working of the drum 11.

A variation of this feature is shown to the right of FIG. 9. It is seen that the pump referenced here by 281 is operable by a connecting rod 30 from an arm 32 ending at a float 33. Here again, the oscillations of the assembly of the arm 4 and the buoy 1 involve corresponding oscillations of the arm 32 actuating the pump 281.

It is self-evident that according to this feature of the invention, any other equipment members could be driven in this manner automatically as a function of the swell.

In the preceding description, it is assumed that the arm 4 was rigidly fixed to the floating body 1, which appears to be the best solution to ensure a good stability of the said body.

Nevertheless, the invention is not limited to this solution, that is to say, in certain cases, it may be assumed, within the scope of the invention, that an articulation, flexible or universal, is provided between floating body and arm, as illustrated at 34 in FIG. 10.

An advantageous application of the preceding feature is that for which it relates to setting up working barges, as shown in FIG. 11.

In the embodiment of FIG. 11, it is seen that the barge l is articulated, universally, at 34 on an arm 4 such as considered above. This barge could include for example, a derrick 35.

The advantage of such an arrangement is that the assembly may be brought to the work-site where anchorage is to be effected with the arm 4 folded underneath the barge, linked with a hoisting cable 36.

On anchorage, and after having fixed on the bed a bed-plate 2, including advantageously guides 37, for positioning in the bottom plate 18 of the pivot, the arm 4 is lowered and it is arranged for the plate 18 to be positioned exactly at the desired spot by being guided by the guides 37, after which the whole is locked in place by bolts 38 (FIG. 12) passing through the said guides. The same operation is carried out in reverse direction, when it is desired to transport the barge to another place.

Such an assembly is particularly easy to manipulate.

According to another feature of the invention, more particularly relating to the case where, an assumed in FIGS. 1 to 9, the buoy or barge 1 is normally rigidly fixed to the arm 4, it is arranged so that, when desired, the linkage between the buoy 1 and the arm 4 may be brought back to an articulation around a horizontal axis, so that thus the arm 4 may be towed in a substantially horizontal direction, as shown in FIG. 13.

To effect such fixing between the elements 1 and 4, any suitable means may be employed. It will generally suffice, on one hand, to provide a sufficiently robust horizontal articulation, whilst in addition there is provided between points such as 41 and 42, mechanical fixing means of any suitable type, adapted to ensure, in the mounted position (FIG. 14), the rigid fixing and locking at 43.

By proceeding in this way, there is avoided, in the towing position, imposing on the buoy 1 an exaggerated slope, the latter remaining, on the contrary, freely in its normal floating position, as shown in FIG. 13.

It is assumed, in FIGS. 13 and 14, that the anchoring base 2 is constituted by one or several hollow bodies capable of being filled with liquid on immersion.

On the contrary, for transportation (FIG. 13), this base-plate 2 can be made floating, so that it supports, at least partly, the weight of the arm 4.

To pass from the towing position of FIG. 13, to the mounting, position of FIG. 14, recourse is hadto any suitable means adapted to support and to ensure the descent of the base 2 and of the arm. These means include for example a winch system 44 supportable by a floating body 45.

However there can also, to ensure this mounting, be used winches borne by a mast or the like on the barge. Such is to be seen in FIG. 15 where a mast of this sort is shown at 35.

It should be noted on the other hand that if instead of a floating body 2, recourse is had to a body of concrete such as shown in FIG. 15 at 2, this anchoring base 2 will be brought in separately so that there will only have to be supported, to ensure towing, the weight of half of the arm 4 as well as the part 17 hearing the vertical pivot 10.

FIGS. 115 and 16 show an assembly also according to the invention, more especially in the case where the floating system is constituted by a barge or a pontoon provided with handling means.

In these figures, there is to be seen:

at 35, a mast capable of being, if necessary, brought into extracted position for mounting (position shown in interrupted line in FIG. 15 or in folded position (position shown in full line),

and at 46 a derrick or other similar device intended to support, and this at a suitable distance from the pontoon,the pipes 12 adapted to ensure the connection with a petroleum ship 47.

There is also seen here at 16, the one or more connecting pipes running the length of the arm 4 and, at 13, the tubes going from a fixed base positioned on the littoral or at any other place.

In this embodiment, the arm 4 is articulated under the pontoon at 34. For transportation, that is to say to bring the device to the work-site or to bring it into port, the arm 4 is brought into a horizontal position by means of the mast 35 and of the corresponding winch.

There is shown, in FIGS. 17 and 18, another embodiment of the invention, according to which the floating system 1 takes the form of an elongated quay, alongside which a ship may be brought and there moored by any mooring means such as shown at 48.

There is also seen here at 16, 12 and 13, the abovementioned pipes.

The one or more arms 4 are articulated at 34 below the floating system 1 forming a quay and, in the course of towing, they can be folded back. under the said quay, the end adjacent to the pivot 17, 10 being lifted by any suitable means such as described above.

It is understood that the floating system 1, for example that of FIGS. 17 and 18, could be produced in any other manner than that shown. Thus it could be constituted by a tubular trellis frame borne by floats. The assembly would thus be lighter and less sensitive to the effects of the swell.

According to another feature of the invention, illustrated in FIGS. 19 to 2l,the connection, between the arm 4 and the anchoring base 2, is effected by a universal articulation, which prevent the arm 4 from turning around its longitudinal axis, which joint is shown at 50 in FIG. 19.

This arrangement is advantageous, since in its appli cation to petroleum installations, with a pipe such as 16 running the length of the arm and bringing petrol from a reservoir on the sea-bed or from an inlet pipe 13, it becomes useless to provide a rotary connection between 13 and 16: in fact, the arm 4 not turning on itself, it suffices to provide a flexible connecting tube 26.

But, due to the fact that the arm 4 does not turn on itself (by reason of the presence of the universal joint), it is necessary to provide additional means to maintain the work-platform 51 of the buoy proper 52, for example, these means consisting in separating the buoy proper from the floating head 1, by a pivoting device 53.

There is clearly seen in FIG. 19 showing two extreme positions of the arm 4 on both sides of the vertical Z-Z passing through the universal joint, that the buoy proper 52 turns around the axis x x of its pivot, when passing from one to the other of these positions.

Generally, this rotation is effected automatically, due to the fact that the center of gravity G of the pivoting buoy 52 will be situated below the axis x x of the said pivot.

But, of course, servo means may be provided to actuate the pivoting around the axis x x, as a function of the rotation of the arm 4 around the axis Z Z.

The foregoing applies to any floating assembly other than a buoy.

Thus, the same feature is applied to a barge or floating quay of the type already described above.

Such a barge is shown at 1, FIGS. 20 and 21.

It constitutes in this case the main floating part, which is connected, by an articulation with a horizontal axis 54, to an intermediate support 55, itself mounted in pivoting manner around an axis x x on a head 56 ending the arm 4.

In the variation of FIG. 20, the articulation 54 is provided on a sort of cradle 57. In the variation of FIG. 21, it is provided on an intermediate part arranged in the same structure of the barge. Any other embodiment may be conceived.

In particular, the head 55, 56, instead of ending at the centre of the barge, could be articulated to one end of the latter.

As a result of which, whatever the embodiment adapted, there are produced floating assemblies of which the operation emerges sufficiently from the preceding description to make it unnecessary to pursue the subject, and which have, with respect to those of the type concerned already existing, and especially in the application to petroleum installations, numerous advantages, especially:

that of enabling, whilst ensuring the stability of the buoys or other floating bodies, their displacements at the surface and in depth being rendered as small as possible under the action of the forces which affects them,

that of enabling their orientation in the wind to be ensured automatically,

and that of avoiding any abnormal forces on the anchoring point, under the action of forces affecting the said floating bodies.

Besides petroleum applications, the invention can be used in any other applications. In particular, it could be applied to buoys intended for marking out navigation channels. A conventional buoy is attached to a chain of which the length is of the order of three times the depth of water, so that its apparent position has an uncertainty equal to the diameter of the width of channel, hence in space of the order of six times the depth of water. With the system according to the invention, the uncertainty can be reduced to twice or three times the depth.

As is self-evident, and as results besides already from the preceding description, the invention is in no way limited to those of its methods of application, nor to those of its methods of production of its various parts, which have been more particularly considered; it embraces, on the contrary, all variations.

What I claim is:

1. System for the mooring of ships, comprising in combination:

a non-self propelled permanently floating unit providing mooring means for a ship,

a rigid arm permanently attached to said floating unit,

an anchoring base having fixing means to fix it to the sea bed,

means connecting said arm to said base pivotally around both a horizontal and a vertical axis,

said arm being adapted to resist forces applied to said floating unit by wind, swell, current and a moored ship,

said system being so-dimensioned so that, taking into account the depth of the sea bed, said arm takes an inclination to the vertical from about to about 45 2. System according to claim 1, wherein the arm is rigidly attached to said floating unit.

3. System according to claim I, wherein the arm is pivotally attached to said floating unit.

4. System according to claim ll, wherein the arm is constituted by a metallic trellis framework.

5. System according to claim ll, wherein the floating unit is shaped as a boat hull.

6. System according to claim 1, wherein the arm provides support and guide means for a pipe, in combination with, close to said base, a rotary joint.

7. System according to claim I, connected to a ground petroleum installation, wherein the system includes a vertical piping device along the axis of the vertical pivot of the base, in combination with bracing arms connecting said piping to the assembly of the arm and the floating unit.

8. System according to claim I, wherein the attachment of said arm to said floating unit is normally rigid but removable for transportation of a system to the work station.

9. System according to claim 1, wherein the attachment of said arm to said floating unit is at least at two points of which one constitutes a horizontal pivoting axis.

10. Method for transporting a jsystem according to claim 9 to a work site, comprising rendering said base buoyant, connecting said floating unit to said base by means of said arm and towing the resulting assembly to the work site.

II. System according to claim 9, said arm being adapted to be hinged to the floating unit at least during towing and placing in position, wherein the floating unit carries lifting appliances for positioning the arm and the base.

12. System according to claim 1, wherein the floating unit is a mooring buoy, wherein said buoy is substantially flat in form.

13. System according to claim 1, wherein the floating unit is a buoy, wherein said buoy is in the form ofa vertical column.

14. System according to claim 13, wherein the column comprises a float of a form flattened at its lower part.

15. System according to claim I, wherein the floating unit is a mooring buoy, said system including at least one winding drum for a flexible tube adapted to be connected to a ship, and said drum being fed from the bed by pipes including articulated joints.

16. System according to claim 15, wherein the feed pipe coming from the bed includes first a vertical extension arranged along the pivoting axis, and a joint is provided at the upper part of said extension to feed a pipe going towards the buoy.

17. System according to claim 15, wherein a single joint is provided at the lower part, on a vertical connection, to ensure the pivoting around the vertical axis.

18. System according to claim I, wherein the pivoting around the vertical axis is ensured by a device of the type of turning plates.

19. System according to claim 1, wherein the equipment is provided on said unit, and actuation of certain at least of said equipment is ensured by a hydraulic motor actuated by a pump automatically manoeuvrable as a function of the swell.

20. System according to claim 19, wherein said pump is borne by the articulated arm and actuated by a tierod connected to the anchoring base.

21. System according to claim 19, wherein the pump is borne by the unit and maneuvered by rod means connected to the pivoting arm borne by the unit and ending at a float resting on the liquid surface.

22. System according to claim 1, wherein the floating unit is a flattened boat, wherein the arm articulated to the base is itself articulated to said barge, in combination with a lifting system to raise the arm for transport during an anchoring period, the end of said arm being capable on anchoring, of being fixed in removable manner on the base previously anchored on the sea bed.

23. System according to claim 1, wherein a mast means is used to bring arm to a horizontal position.

24. System according to claim 23, wherein said mast means is foldable.

25. System according to claim 1, wherein the floating unit is made to include at least one support arm extending outwardly and intended to support flexible pipes ensuring the connection with a ship.

26. System according to claim 1, wherein the floating unit is in the form of a floating quay beneath which the arm is articulated.

27. Floating system, according to claim 1, wherein the articulation of the arm on the base is of the universal joint type, so that the arm does not turn around its longitudinal axis.

28. System according to claim 27, wherein at least part of the floating unit mounted at the end of the arm, is mounted in pivoting manner on said arm, around a longitudinal axis with respect to the latter.

29. System according to claim 28, wherein the rotation of said part arranged at the end of the arm is pivoted automatically by gravity.

30. System according to claim 28, including a servo system adapted to pivot said part arranged at the end of the arm, as a function of the pivoting of the arm around the vertical axis passing through its lower articulation.

31. System according to claim 28, wherein said part of the unit is connected in pivoting manner to a floating head borne at the end of the arm.

32. System according to claim 1, wherein at least part of the floating unit mounted at the end of the arm, is mounted in pivoting manner on said arm, around a 1ongitudinal axis with respect to the latter, comprising a barge, wherein the barge is connected, in articulated manner around a horizontal axis, to a support mounted at the end of the arm and pivotable: with respect to the latter around an axis longitudinal to said arm. 

1. System for the mooring of ships, comprising in combination: a non-self propelled permanently floating unit providing mooring means for a ship, a rigid arm permanently attached to said floating unit, an anchoring base having fixing means to fix it to the sea bed, means connecting said arm to said base pivotally around both a horizontal and a vertical axis, said Arm being adapted to resist forces applied to said floating unit by wind, swell, current and a moored ship, said system being so-dimensioned so that, taking into account the depth of the sea bed, said arm takes an inclination to the vertical from about 20* to about 45 *.
 2. System according to claim 1, wherein the arm is rigidly attached to said floating unit.
 3. System according to claim 1, wherein the arm is pivotally attached to said floating unit.
 4. System according to claim 1, wherein the arm is constituted by a metallic trellis framework.
 5. System according to claim 1, wherein the floating unit is shaped as a boat hull.
 6. System according to claim 1, wherein the arm provides support and guide means for a pipe, in combination with, close to said base, a rotary joint.
 7. System according to claim 1, connected to a ground petroleum installation, wherein the system includes a vertical piping device along the axis of the vertical pivot of the base, in combination with bracing arms connecting said piping to the assembly of the arm and the floating unit.
 8. System according to claim 1, wherein the attachment of said arm to said floating unit is normally rigid but removable for transportation of a system to the work station.
 9. System according to claim 1, wherein the attachment of said arm to said floating unit is at least at two points of which one constitutes a horizontal pivoting axis.
 10. Method for transporting a jsystem according to claim 9 to a work site, comprising rendering said base buoyant, connecting said floating unit to said base by means of said arm and towing the resulting assembly to the work site.
 11. System according to claim 9, said arm being adapted to be hinged to the floating unit at least during towing and placing in position, wherein the floating unit carries lifting appliances for positioning the arm and the base.
 12. System according to claim 1, wherein the floating unit is a mooring buoy, wherein said buoy is substantially flat in form.
 13. System according to claim 1, wherein the floating unit is a buoy, wherein said buoy is in the form of a vertical column.
 14. System according to claim 13, wherein the column comprises a float of a form flattened at its lower part.
 15. System according to claim 1, wherein the floating unit is a mooring buoy, said system including at least one winding drum for a flexible tube adapted to be connected to a ship, and said drum being fed from the bed by pipes including articulated joints.
 16. System according to claim 15, wherein the feed pipe coming from the bed includes first a vertical extension arranged along the pivoting axis, and a joint is provided at the upper part of said extension to feed a pipe going towards the buoy.
 17. System according to claim 15, wherein a single joint is provided at the lower part, on a vertical connection, to ensure the pivoting around the vertical axis.
 18. System according to claim 1, wherein the pivoting around the vertical axis is ensured by a device of the type of turning plates.
 19. System according to claim 1, wherein the equipment is provided on said unit, and actuation of certain at least of said equipment is ensured by a hydraulic motor actuated by a pump automatically manoeuvrable as a function of the swell.
 20. System according to claim 19, wherein said pump is borne by the articulated arm and actuated by a tie-rod connected to the anchoring base.
 21. System according to claim 19, wherein the pump is borne by the unit and maneuvered by rod means connected to the pivoting arm borne by the unit and ending at a float resting on the liquid surface.
 22. System according to claim 1, wherein the floating unit is a flattened boat, wherein the arm articulated to the base is itself articulated to said barge, in combination with a lifting system to raise the arm for transport during an anchoring period, the end of said arm being capable on anchoring, of being fixed in removable manner on tHe base previously anchored on the sea bed.
 23. System according to claim 1, wherein a mast means is used to bring arm to a horizontal position.
 24. System according to claim 23, wherein said mast means is foldable.
 25. System according to claim 1, wherein the floating unit is made to include at least one support arm extending outwardly and intended to support flexible pipes ensuring the connection with a ship.
 26. System according to claim 1, wherein the floating unit is in the form of a floating quay beneath which the arm is articulated.
 27. Floating system, according to claim 1, wherein the articulation of the arm on the base is of the universal joint type, so that the arm does not turn around its longitudinal axis.
 28. System according to claim 27, wherein at least part of the floating unit mounted at the end of the arm, is mounted in pivoting manner on said arm, around a longitudinal axis with respect to the latter.
 29. System according to claim 28, wherein the rotation of said part arranged at the end of the arm is pivoted automatically by gravity.
 30. System according to claim 28, including a servo system adapted to pivot said part arranged at the end of the arm, as a function of the pivoting of the arm around the vertical axis passing through its lower articulation.
 31. System according to claim 28, wherein said part of the unit is connected in pivoting manner to a floating head borne at the end of the arm.
 32. System according to claim 1, wherein at least part of the floating unit mounted at the end of the arm, is mounted in pivoting manner on said arm, around a longitudinal axis with respect to the latter, comprising a barge, wherein the barge is connected, in articulated manner around a horizontal axis, to a support mounted at the end of the arm and pivotable with respect to the latter around an axis longitudinal to said arm. 